/**
 * Created by luwenzheng on 2015/7/16.
 */
function draw(id){
    var canvas = document.getElementById(id);
    var context = canvas.getContext('2d');
    context.fillStyle = "#f1f2f3";
    context.fillRect(0,0,400,400);
    for(var i = 0; i < 10; i++){
        context.beginPath();
        context.arc(i*25,i*25,i*10,0,Math.PI*2,true);
        context.closePath();
        context.fillStyle = "rgba(255,0,0,0.25)";
        context.fill();
    }

}